This invention relates to vacuum holddown apparatus for stabilizing media, and their method of operation in hard copy devices.
Hard copy devices process images on media, typically taking the form of printers, plotters (employing inkjet or electron photography imaging technology), scanners, facsimile machines, laminating devices, and various combinations thereof, to name a few. These hard copy devices typically transport media in a sheet form from a supply of cut sheets or a roll to an interaction zone where printing, scanning or post-print processing, such as laminating, overcoating or folding occurs. Often different types of media are supplied from different supply sources, such as those containing plain paper, letterhead, transparencies, pre-printed media, etc.
In some kinds of hard copy apparatus a vacuum apparatus is used to apply a suction or vacuum force to a sheet of flexible media to adhere the sheet to a surface or to stabilize the sheet relative to the surface, for example, for holding a sheet of print media temporarily to a platen. Such vacuum holddown systems are a relatively common, economical technology to implement commercially and can improve machine throughput specifications and the quality of the print job. There are numerous kinds of vacuum platen systems. For example, in ink-jet printers it is known to utilize a rotating drum with holes through the drum surface so that a vacuum through the drum cylinder provides a suction force at the holes in the drum surface. The suction force adheres a sheet of media to the drum surface in order to improve the quality of the print job.
A vacuum holddown for a hard copy device comprises a platen having an upper surface and plural vacuum zones arranged in a side-by-side array across the platen. Each vacuum zone is coupled to a vacuum source. Each vacuum zone defines a cavity in the upper surface of the platen and each vacuum zone includes a port fluidly coupled to the vacuum source. Each vacuum zone is defined by a back wall and opposed side walls and an open end.